Amazing stuff!
"Chinese researchers say they’ve created the first pure samples of hexagonal diamond, a superhard mineral previously found only in meteorites, that outperforms natural diamond in hardness and heat resistance."
From the abstract:
"Known as the ‘ultimate semiconductor’, cubic diamond (CD) has gained substantial interest both scientifically and industrially. Its polymorph, hexagonal diamond (HD), is even more intriguing because of its fascinating properties associated with the meteorite impacts. As no solid experimental evidence has been provided to prove its existence, the physical properties of HD remain largely unexplored.
Here we report the synthesis of millimetre-sized, phase-pure HD from highly oriented pyrolytic graphite (HOPG) compressed along the c-axis at elevated temperatures. Combining advanced structural characterizations and theoretical simulations, we confirm the identity of HD and clarify the transformation pathway from graphite. Bulk HD exhibits a slightly higher hardness than CD and high thermal stability. These findings resolve the long-standing controversy on the existence of HD as a discrete carbon phase and provide new insight into the graphite-to-diamond phase transition, paving the way for future research and practical use of HD in advanced technological applications."
Bulk hexagonal diamond (no public access)
Fig. 2: Atomic structure of the bulk HD recovered from 20 GPa and 1,300 °C.
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